An increased interest has recently developed for advanced sound reproduction systems capable of providing different sound in different spatial portions of a listening room. In this context, the concept of (individual) sound zones has been developed. That is, at least two different sound zones are provided within one (coherent) listening room, wherein the sound to be reproduced in each sound zone (and presented to the listeners present in the respective zone) may be different. In this regard, different sound is to be understood as different audio content (e.g., two different radio programs) or different sound settings (treble, bass, etc.) for different sound zones. It should be noted that the sound signal to be reproduced in a specific sound zone may also be zero to create a silent sound zone.
When reproducing different sound signals in different spatially separated sound zones, one important feature is to “limit” the acoustic sound signal designated for a specific sound zone to that specific sound zone and to prevent “crosstalk” to a neighboring sound zone. Theoretical work (D. H. Cooper, J. L. Bauck: “Prospects for Transaural Recording”, in: J. Audio Eng. Soc., Vol. 37, No. 1/2, January/February 1989) has shown that crosstalk cancellation is possible using inverse filters. Feasible practical implementations are so-called “transaural stereo” systems, which compensate for the crosstalk from the left audio channel to the right ear of the listener and vice versa using inverse filters. This concept may theoretically be applied to multi-dimensional cases. However, practical implementations are often not feasible due to the complexity of the filter design of the mentioned (multi-dimensional) inverse filters.
Listening rooms may be, for example, domestic rooms or the interior of automobiles (car cabins). Particularly in the market of upper-class automobiles, an increasing demand for high-quality audio reproduction has been determined, which includes the reproduction of different sound signals in different sound zones, wherein a sound zone is usually associated with a specific person present in the automobile. For example, four different sound zones may be provided within a car cabin: one for the driver, one for the front passenger and one for each of the two rear passengers.
Thus, there is a general need for sound reproduction systems that enable multiple sound zones within a listening room.